/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_mat_mult_fast_q31.c
*
* Description:	 Q31 matrix multiplication (fast variant).
*
* Target Processor: Cortex-M4/Cortex-M3
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupMatrix
 */

/**
 * @addtogroup MatrixMult
 * @{
 */

/**
 * @brief Q31 matrix multiplication (fast variant) for Cortex-M3 and Cortex-M4
 * @param[in]       *pSrcA points to the first input matrix structure
 * @param[in]       *pSrcB points to the second input matrix structure
 * @param[out]      *pDst points to output matrix structure
 * @return     		The function returns either
 * <code>ARM_MATH_SIZE_MISMATCH</code> or <code>ARM_MATH_SUCCESS</code> based on the outcome of size checking.
 *
 * @details
 * <b>Scaling and Overflow Behavior:</b>
 *
 * \par
 * The difference between the function arm_mat_mult_q31() and this fast variant is that
 * the fast variant use a 32-bit rather than a 64-bit accumulator.
 * The result of each 1.31 x 1.31 multiplication is truncated to
 * 2.30 format. These intermediate results are accumulated in a 32-bit register in 2.30
 * format. Finally, the accumulator is saturated and converted to a 1.31 result.
 *
 * \par
 * The fast version has the same overflow behavior as the standard version but provides
 * less precision since it discards the low 32 bits of each multiplication result.
 * In order to avoid overflows completely the input signals must be scaled down.
 * Scale down one of the input matrices by log2(numColsA) bits to
 * avoid overflows, as a total of numColsA additions are computed internally for each
 * output element.
 *
 * \par
 * See <code>arm_mat_mult_q31()</code> for a slower implementation of this function
 * which uses 64-bit accumulation to provide higher precision.
 */

arm_status arm_mat_mult_fast_q31(
    const arm_matrix_instance_q31* pSrcA,
    const arm_matrix_instance_q31* pSrcB,
    arm_matrix_instance_q31* pDst)
{
	q31_t* pIn1 = pSrcA->pData;                    /* input data matrix pointer A */
	q31_t* pIn2 = pSrcB->pData;                    /* input data matrix pointer B */
	q31_t* pInA = pSrcA->pData;                    /* input data matrix pointer A */
//  q31_t *pSrcB = pSrcB->pData;                    /* input data matrix pointer B */
	q31_t* pOut = pDst->pData;                     /* output data matrix pointer */
	q31_t* px;                                     /* Temporary output data matrix pointer */
	q31_t sum;                                     /* Accumulator */
	uint16_t numRowsA = pSrcA->numRows;            /* number of rows of input matrix A    */
	uint16_t numColsB = pSrcB->numCols;            /* number of columns of input matrix B */
	uint16_t numColsA = pSrcA->numCols;            /* number of columns of input matrix A */
	uint16_t col, i = 0u, j, row = numRowsA, colCnt;      /* loop counters */
	arm_status status;                             /* status of matrix multiplication */
	q31_t inA1, inA2, inA3, inA4, inB1, inB2, inB3, inB4;

#ifdef ARM_MATH_MATRIX_CHECK


	/* Check for matrix mismatch condition */
	if((pSrcA->numCols != pSrcB->numRows) ||
	        (pSrcA->numRows != pDst->numRows) || (pSrcB->numCols != pDst->numCols)) {
		/* Set status as ARM_MATH_SIZE_MISMATCH */
		status = ARM_MATH_SIZE_MISMATCH;
	} else
#endif /*      #ifdef ARM_MATH_MATRIX_CHECK    */

	{
		/* The following loop performs the dot-product of each row in pSrcA with each column in pSrcB */
		/* row loop */
		do {
			/* Output pointer is set to starting address of the row being processed */
			px = pOut + i;

			/* For every row wise process, the column loop counter is to be initiated */
			col = numColsB;

			/* For every row wise process, the pIn2 pointer is set
			 ** to the starting address of the pSrcB data */
			pIn2 = pSrcB->pData;

			j = 0u;

			/* column loop */
			do {
				/* Set the variable sum, that acts as accumulator, to zero */
				sum = 0;

				/* Initiate the pointer pIn1 to point to the starting address of pInA */
				pIn1 = pInA;

				/* Apply loop unrolling and compute 4 MACs simultaneously. */
				colCnt = numColsA >> 2;


				/* matrix multiplication */
				while(colCnt > 0u) {
					/* c(m,n) = a(1,1)*b(1,1) + a(1,2) * b(2,1) + .... + a(m,p)*b(p,n) */
					/* Perform the multiply-accumulates */
					inB1 = *pIn2;
					pIn2 += numColsB;

					inA1 = pIn1[0];
					inA2 = pIn1[1];

					inB2 = *pIn2;
					pIn2 += numColsB;

					inB3 = *pIn2;
					pIn2 += numColsB;

					sum = (q31_t)((((q63_t) sum << 32) + ((q63_t) inA1 * inB1)) >> 32);
					sum = (q31_t)((((q63_t) sum << 32) + ((q63_t) inA2 * inB2)) >> 32);

					inA3 = pIn1[2];
					inA4 = pIn1[3];

					inB4 = *pIn2;
					pIn2 += numColsB;

					sum = (q31_t)((((q63_t) sum << 32) + ((q63_t) inA3 * inB3)) >> 32);
					sum = (q31_t)((((q63_t) sum << 32) + ((q63_t) inA4 * inB4)) >> 32);

					pIn1 += 4u;

					/* Decrement the loop counter */
					colCnt--;
				}

				/* If the columns of pSrcA is not a multiple of 4, compute any remaining output samples here.
				 ** No loop unrolling is used. */
				colCnt = numColsA % 0x4u;

				while(colCnt > 0u) {
					/* c(m,n) = a(1,1)*b(1,1) + a(1,2) * b(2,1) + .... + a(m,p)*b(p,n) */
					/* Perform the multiply-accumulates */
					sum = (q31_t)((((q63_t) sum << 32) +
					               ((q63_t) * pIn1++ * (*pIn2))) >> 32);
					pIn2 += numColsB;

					/* Decrement the loop counter */
					colCnt--;
				}

				/* Convert the result from 2.30 to 1.31 format and store in destination buffer */
				*px++ = sum << 1;

				/* Update the pointer pIn2 to point to the  starting address of the next column */
				j++;
				pIn2 = pSrcB->pData + j;

				/* Decrement the column loop counter */
				col--;

			} while(col > 0u);

			/* Update the pointer pInA to point to the  starting address of the next row */
			i = i + numColsB;
			pInA = pInA + numColsA;

			/* Decrement the row loop counter */
			row--;

		} while(row > 0u);

		/* set status as ARM_MATH_SUCCESS */
		status = ARM_MATH_SUCCESS;
	}

	/* Return to application */
	return (status);
}

/**
 * @} end of MatrixMult group
 */
